The manuscript show the results obtained with a new methodology: to apportion source contributions (shipping, vehicular, residential heating, industrial) and study optical properties variation of BrC species due to atmospheric aging. This methodology, named INTERPLAY, integrates multi-year aerosol observations with air mass back-trajectories and emission inventories.

The paper is very good, showing interesting and sounding results that can be useful at different scientific and technical levels. The manuscript very well written and clear in every part.

General comment: the results obtained following the INTERPLAY approach are well discussed, with a focus on BrC lifetime, as well as the comparison with the output of the Aethalometer model. However, the manuscript lacks sufficient information on the model itself, effectively making it impossible for another researcher to attempt to replicate it in another context. While this is understandable (given that this is a research article), my personal position is that this powerful tool should (anyway) be better described in §2.5, with the basic technical details in the supplement.

Specific comments:

Line 14: I would explain also in the abstract what “ATOLL” stands for.

Line 31: Why is “Light Absorbing Carbonaceous particles” acronym written in capital letters (LAC) while “Aerosol-Radiation Interaction” acronym (ari) in lowercase? Same for aci.

Line 308: do the Authors intend “AAEff” and “AAEwb” instead of “BCff” and “BCwb”? I suspect there is some confusion here. BC, optically speaking, is something with the AAE close to 1 by definition, and the deviation from this value depends mainly on the mixing/coating state/size distribution. Other things are BC from fossil fuel combustion (BCff) and by wood burning (BCwb). Together they form BC (BCff + BCwb = BC). But BCwb has an AAEwb close to 1 since it is still BC. In the literature are reported values of AAEwb up to 11, but (as done in the present paper) a value of 2 is generally accepted. But this value (AAEwb) is not characteristic of BCwb alone nor of the BrC present in the PM produced by wood combustion: it is an “effective average value” between AAE_BCwb and AAE_BrC, as well as the most critical parameter to be set in the Aethalometer model. Please take care of the differences between absorption coefficients apportioned by the Aethalometer model (babs_ff, babs_wb), related masses BC_ff, BC_wb, and spectral dependencies of the light absorbing species AAE_ff, AAE_wb, AAE_BC and AAE_BrC and consider revising this part. I actually suggest having a look at the following paper: Multi-wavelength optical determination of black and brown carbon in atmospheric aerosols, https://doi.org/10.1016/j.atmosenv.2015.02.058.

Review research article: ar-2024-5

The manuscript titled “Assessment of light-adsorbing carbonaceous aerosol origins and properties at the ATOLL site in Northern France” apportions, by using the INTERPLAY integrated multi-step approach (with back trajectories and emission inventories, in-situ measurements), sources (shipping, vehicular, residential heating, industrial) of BC and BrC and their lifecycles, focusing on effect of aging processes on optical properties of BrC.

The manuscript is well structured and written, the research question is properly outlined and clearly addressed. Also, the methodology is exhaustively explained and consistent with the main objectives. References are appropriate and key studies included. The topic and the submitted study is very interesting, for the experimental integrated approach, and complete in discussing obtained results.

In my opinion, the study is valuable and could have a very good research sound for the research community, needing only some little refinements.

General comments

The applied approach is innovative, with uncertainties discussed in the conclusions, and easily scalable, being based on available/easily accessible data.

Apart from mentioning previous studies performed at ATOLL site and in Paris, are there other European sites with same measurements types to be compared? Please, report some of them and discuss results.

Line 163: according to which criterion is a minimum contribution of 20% of the total integrated BC chosen? Please provide references, in case some studies applied it before.

The authors could have a look at these papers, about other sites belonging to the ACTRIS network: https://doi.org/10.1016/j.atmosres.2017.10.004; https://doi.org/10.1016/j.atmosres.2020.104976.

Minor revisions

• The first and last statements of the abstract are almost equal. Delete one of them.
• Regarding lifecycle of LAC, take a look at “Liu, D., He, C., Schwarz, J.P. et al. Lifecycle of light-absorbing carbonaceous aerosols in the atmosphere. npj Clim Atmos Sci 3, 40 (2020). https://doi.org/10.1038/s41612-020-00145-8”
• Check citation style throughout the text (i.e., missing commas).
• Line 124: why are not world-historical trend of emission inventory extended until 2019 (study period)?
• Does France include Lille or not in the pie-charts of the Figures 2b and 3a, 3b?
• Line 260: Figure S7 is wrongly indicated as Figure S5.
• Line 335-336: sentence to be re-phrase.
• Line 371-372: re-phrase the sentence for missing verb.
• Figure S1: check incorrect figure numbering and caption.
• Figure S7 could be moved as Figure S6.